1. Field of the Invention
The present invention relates to a control system for a motor-assisted bicycle, particularly to a control for a motor-assisted bicycle which works mechanically.
2. Description of Related Art
Nowadays, the main source of air pollution is exhaust gas generated by traffic vehicles. The problem of air pollution has become increasingly grave, and demand for traffic vehicles not polluting the air is more and more urgent.
Obviously, bicycles are most suitable vehicles for pollution-free traffic. However, riding a bicycles entirely relies on human effort and thus has physical limitations. Bicycles are not suitable for long distances. A conventional bicycle has a chain wheel and a sprocket which have widely differing numbers of teeth. Therefore accelerating the bicycle is hard, and cycling uphill, especially at steep climbing angles, forces a cyclist to get off and to push the bicycle.
To compensate for the shortcomings of conventional bicycles at long distances and when starting or going uphill, motor-assisted bicycles have appeared. A motor-assisted bicycles mostly uses an electric motor, providing additional power for accelerating and climbing, so that the cyclist will not be strained when accelerating or going uphill.
The ideas of a motor-assisted bicycle and of an electrically driven motorcycles are different. A motor-assisted bicycle relies on a mixture of human and electric power, with electric power supplementing human power when starting, accelerating or climbing. On a level street, less or no supplemental electric power is needed. Downhill, electric power is completely unnecessary, and human physical power as well as electric power are saved.
Therefore, for a motor-assisted bicycle a motor and a battery of minimum size are sufficient and will not add much weight to the bicycle. For proper operation, instant and correct sensing of load during cycling needs to be available to control output of electric power.
Conventional control systems for motor-assisted bicycles mainly divide in torsion control systems, speed measuring systems, combined torsion and speed measuring systems, and manual systems. Each of these types of control systems gather signals which are fed into a microcomputer where output signals are generated for controlling electric power output.
Motor assisted bicycles are designed according to needs of environmental protection. However, control systems thereof still have many problems.
First, conventional control systems for motor-assisted bicycles need a complicated controller with software to control electric output power, which is expensive. Moreover, control by a microcomputer is not capable to adapt completely to changes of load during cling. Therefore, starting the bicycle or climbing will not lead to an immediate response in electric power output and thus are not well dealt with.
Furthermore, conventional control systems for motor-assisted bicycles control electric power output according to a linear curve or only by switching on and off. Thus slight loads lead to full electric power or superfluous output thereof, wasting electric energy and reducing mileage.
Furthermore, conventional control systems for motor-assisted bicycles react only slowly to load changes. Then slow starting reactions set in, and, on the other hand, switching off of electric power in the event of sudden braking is belated. This leads to extended braking ranges and the risk of skidding.
Finally, conventional control systems for motor-assisted bicycles are not adjustable, having software that follows fixed control patterns. Changing the control behavior of a conventional control system is difficult. Yet there is a need to adapt the control behavior to various users, e.g., robust cyclists who want to exercise, where electric energy is wasted, or weaker cyclists demanding more assistance.
Therefore, conventional control systems for motor-assisted bicycles do not control electric power output in a satisfactory way. For this reason, some conventional control systems provide an extra manual switch for additional control. However, this complicates conventional control systems even more and makes usage more awkward.
It is the main object of the present invention to provide a control system for a motor-assisted bicycle which is simple and inexpensive.
Another object of the present invention is to provide a control system for a motor-assisted bicycle which instantly measures load changes and generates quick responses to assist starting and climbing effectively while saving energy.
A further object of the present invention is to provide a control system for a motor-assisted bicycle which is adaptable to various users with various physical demands and cycling behavior patterns thereof.
The present invention can be more fully understood by reference to the following description and accompanying drawings.